Catalytic processes for the conversion of hydrocarbons are well known and extensively used. Invariably the catalyst used in these processes becomes deactivated for one or more reasons. Where the accumulation of coke deposits causes the deactivation, reconditioning of the catalyst to remove coke deposits restores the activity of the catalyst. Coke is normally removed from catalyst by a regeneration operation that contacts the coke containing catalyst at high temperature with an oxygen containing gas to combustively remove the coke. Regeneration may be carried out in-situ or the catalyst may be removed from a vessel in which the hydrocarbon conversion takes place and transported to a separate regeneration zone for coke removal. Arrangements for continuously or semi-continuously removing catalyst particles from a reaction zone for coke removal in a regeneration zone are well known.
In continuous or semi-continuous regeneration processes, catalyst particles are at least periodically added and withdrawn from a bed of catalyst in which the coke is combusted. Regions of intense burning that extend through portions of the catalyst bed develop as the coke is combusted. After this intense burning, certain catalysts require reconditioning to restore their effectiveness. For example reforming catalysts typically contain halogens, such as chloride compounds, and noble metals, usually platinum. These catalysts require reconditioning to restore the activity of the noble metal to its most highly catalytic state and to replace the halogen on the catalyst that may be lost in the reaction zone or through the combustion of coke. Reconditioning for a reforming catalyst will include contact with a halogen containing compound, to redistribute the platinum metal and replace the halogen that may be lost from the catalyst, followed by a drying step to reduce the moisture content of the catalyst. Consequently, catalyst residence time, flow rate, temperature and halogen mixing are critical variables for optimal catalyst performance.
Typically, regeneration of catalyst particles is performed in a single vessel including a coke combustion zone, a halogenation zone and a drying zone. The catalyst particles move downward under the force of gravity through the vessel while a combustion gas, halogenation gas, and drying gas move upward through selected zones. Often, the halogenation gas is added to the drying gas within an interzone tunnel in the vessel and is fed into the halogenation zone. Such an arrangement may cause reduced catalyst bed volume for catalyst particle flow and reduced catalyst resident time. Catalyst residence time in the halogenation zone is a key variable for reconditioning the catalyst to its most highly active state. Further, such an arrangement may require a larger vessel to provide a desired residence time and rate of regeneration, leading to increased expense. Also, as the external halogenation piping loop increases, heat loss increases, leading to added expense for maintaining targeted temperatures.
Accordingly, it is desirable to provide methods and apparatuses for regenerating catalyst particles in a vessel that remove a drying gas from the vessel at a drying zone and that reintroduce the drying gas to the vessel at a halogenation zone. In addition, it is desirable to develop methods and apparatuses for efficiently regenerating catalyst particles with appropriate catalyst resident times while minimizing vessel size. Furthermore, other desirable features and characteristics of the present embodiment will become apparent from the subsequent detailed description and the appended claims, taken in conjunction with the accompanying drawings and this background.